U.S. patent number 6,510,022 [Application Number 09/504,969] was granted by the patent office on 2003-01-21 for method for shaping pole pieces of magnetic heads by chemical mechanical polishing.
This patent grant is currently assigned to International Business Machines Corporation. Invention is credited to Ashok Lahiri, Edward Hin Pong Lee, Eric James Lee, Hong Xu.
United States Patent |
6,510,022 |
Lahiri , et al. |
January 21, 2003 |
Method for shaping pole pieces of magnetic heads by chemical
mechanical polishing
Abstract
The thin film magnetic head of the present invention includes an
improved P2 pole tip/yoke interface structure. The interface
structure includes yoke material that is formed in a concave curved
shape at the interface between the P2 pole tip and the yoke, such
that a right angle interface between the P2 pole tip and the yoke
is eliminated. The process for forming the P2 pole tip/yoke
interface includes a second CMP polishing step that is performed on
the surface of the write head wafer subsequent to the plating of
the P2 pole tip thereon, and subsequent to a first CMP step. This
second CMP step utilizes a relatively soft polishing pad and an
acidic polishing slurry having a pH within the range of
approximately 1 to approximately 5, and preferably approximately
2.5. The acidic polishing slurry contains a chemical agent which
preferentially attacks the P2 pole tip material, such that the
second CMP step results in the recession of the upper surface of
the P2 pole tip relative to the dielectric layer surrounding it, as
well as the significant rounding of the upper edges of the
dielectric trench in which the P2 pole tip is formed. Thereafter,
when the yoke is plated onto the P2 pole tip the rounded upper
edges of the dielectric trench result in a concave curved interface
between the yoke and the P2 pole tip. The resulting P2 pole
tip/yoke interface possesses improved magnetic flux flow control
properties and results in decreased side writing. Greater track per
inch areal data storage results from the reduced side writing of
the improved write head.
Inventors: |
Lahiri; Ashok (Mainz,
DE), Lee; Edward Hin Pong (San Jose, CA), Lee;
Eric James (San Jose, CA), Xu; Hong (San Jose, CA) |
Assignee: |
International Business Machines
Corporation (Armonk, NY)
|
Family
ID: |
24008470 |
Appl.
No.: |
09/504,969 |
Filed: |
February 15, 2000 |
Current U.S.
Class: |
360/125.56;
360/125.57; 360/125.58; G9B/5.082; G9B/5.086 |
Current CPC
Class: |
G11B
5/3116 (20130101); G11B 5/313 (20130101); G11B
5/012 (20130101); Y10T 29/49044 (20150115); Y10T
29/49052 (20150115); Y10T 29/49046 (20150115); Y10T
29/49048 (20150115); Y10T 29/49043 (20150115); Y10T
29/49032 (20150115); Y10T 29/49041 (20150115) |
Current International
Class: |
G11B
5/31 (20060101); G11B 5/012 (20060101); G11B
005/147 () |
Field of
Search: |
;360/126,122,125,317,318,234.1,234.2,234.3 ;29/603.13,603.14,603.15
;204/192.2 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Nguyen; Hoa T.
Assistant Examiner: Tianjie; Chen
Attorney, Agent or Firm: Guillot; Robert O. Intellectual
Property Law Offices
Claims
What is claimed is:
1. A thin film magnetic head including a slider body having an ABS
surface side, comprising: a P1 pole having a first surface that is
formed proximate said slider body and a second surface that is
forward away from said slider body; a gap layer being formed
proximate said second surface of said P1 pole; a P2 pole tip being
formed upon said gap layer, said P2 pole tip being disposed within
a first insulation layer; a yoke member being magnetically engaged
with said P2 pole tip at an interface that is disposed in part on
the ABS surface side, said yoke member being disposed within a
second insulation layer, said interface including a concave surface
shape portion of said yoke member, said concave surface shape
portion of said yoke member being disposed to make contact with
said first insulation layer.
2. A thin film magnetic head as described in claim 1 wherein said
concave surface shape is formed in an external surface of said yoke
member proximate the location of said magnetic engagement of said
yoke member with said P2 pole tip.
3. A thin film magnetic head as described in claim 2 wherein said
concave surface has a radius of curvature of approximately 0.3
microns.
4. A thin film magnetic head as described in claim 3 wherein said
P2 pole tip has a width of approximately 1 micron, and wherein said
P2 pole tip is disposed upon a flat gap layer having flat surface
portions that extend beyond said P2 pole tip, and wherein said
first insulation layer is disposed upon said flat surface portions
of said gap layer.
5. A thin film magnetic head as described in claim 2 wherein said
concave surface shape is formed proximate all edges of said yoke
member that engage said P2 pole tip.
6. A hard disk drive, comprising: at least one hard disk being
adapted for rotary motion upon a drive device; at least one slider
device having a slider body portion being adapted to fly over said
hard disk; a magnetic head having an ABS surface side being formed
on said slider body for writing data on said hard disk; said
magnetic head including: a P1 pole having a first surface that is
formed proximate said slider body and a second surface that is
formed away from said slider body; a gap layer that is formed
proximate said second surface of said P1 pole; a P2 pole tip being
formed upon said gap layer, said P2 pole tip being disposed within
a first insulation layer; a yoke member being magnetically engaged
with said P2 pole tip at an interface that is disposed in part on
the ABS surface side, said yoke member being disposed within a
second insulation layer, said interface including a concave surface
shape portion of said yoke member, said concave surface shape
portion of said yoke member being disposed to make contact with
said first insulation layer.
7. A hard disk drive as described in claim 6 wherein said concave
surface shape is formed in an external surface of said yoke member
proximate the location of said magnetic engagement of said yoke
member with said P2 pole tip.
8. A hard disk drive as described in claim 7 wherein said concave
surface has a radius of curvature of approximately 0.3 microns.
9. A hard disk drive as described in claim 8 wherein said P2 pole
tip has a width of approximately 1 micron, and wherein said P2 pole
tip is disposed upon a flat gap layer having flat surface portions
that extend beyond said P2 pole tip, and wherein said first
insulation layer is disposed upon said flat surface portions of
said gap layer.
10. A hard disk drive as described in claim 7 wherein said concave
surface shape is formed proximate all edges of said yoke member
that engage said P2 pole tip.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to thin film magnetic heads
and methods for manufacturing such heads, and more particularly to
the features of the P2 pole tip/yoke interface of thin film
magnetic write head elements and methods for manufacturing the P2
pole tip/yoke interface.
2. Description of the Prior Art
The well known basic components of thin film magnetic write heads
include a first pole (P1), a write gap layer, a narrow P2 pole tip,
a yoke that is electromagnetically engaged with the P2 pole tip,
and electromagnetic coils that generate a magnetic flux that flows
between the P1 pole and the P2 pole tip. The width of the P2 pole
tip generally defines the track width of the data bits written by
the write head. The yoke is generally significantly wider and
thicker than the P2 pole tip and it serves to control and focus the
flow of magnetic flux generated by the electromagnetic coils of the
write head into the P2 pole tip. The flow of magnetic flux between
the P1 pole and the P2 pole tip across the write gap influences the
magnetic media disposed proximate the write head to record flux
changes therein as data bits. Thus, a significant performance
characteristic of write heads is the proper controlled flow of
magnetic flux from the yoke into the P2 pole tip and across the
write gap. Where the magnetic flux flow control is faulty, the
magnetic flux can flow directly from the yoke to the P1 pole
without passing through the P2 pole tip. This undesirable effect is
termed "side writing" as it creates an undesirable noise band on
each side of the data track that is written by the P2 pole tip, and
the existence and width of the undesirable side band affects the
spacing between the data tracks. Where side writing is minimized,
such that the width of the side bands is minimized, data tracks can
be written closer together such that more tracks per inch (TPI) can
be written and the areal data storage of the magnetic media can be
increased.
In prior art pole tips of various designs, the P2 pole tip/yoke
interface is characterized as a "T" interface. That is, the P2 pole
tip is the downward leg of the "T" and the yoke is formed flatly
and squarely on top of the P2 pole tip leg. Thus the inner angle
between the P2 pole tip and the yoke is approximately a right
angle. This right angle P2 pole tip/yoke interface results in less
than optimum magnetic flux flow control between the yoke and the P2
pole tip. That is, flow of magnetic flux is somewhat inhibited at
the right angle interface, and this can result in side writing when
the magnetic flux flows directly from the yoke to the P1 pole,
rather than flowing through the P2 pole tip. It is therefore
possible to improve the flow of magnetic flux through the P2 pole
tip/yoke interface and thus reduce side writing by shaping the
interface to remove the right angle joinder of the yoke to the P2
pole tip. The present invention is a write head that includes such
an improved P2 pole tip/yoke interface, together with a process for
manufacturing it.
SUMMARY OF THE INVENTION
The thin film magnetic head of the present invention includes an
improved P2 pole tip/yoke interface structure. The interface
structure includes yoke material that is formed in a concave curved
shape at the interface between the P2 pole tip and the yoke, such
that a right angle interface between the P2 pole tip and the yoke
is eliminated.
The process for forming the P2 pole tip/yoke interface includes a
second CMP polishing step that is performed on the surface of the
write head wafer subsequent to the plating of the P2 pole tip
thereon, and subsequent to a first CMP step. This second CMP step
utilizes a relatively soft polishing pad and an acidic polishing
slurry having a pH within the range of approximately 1 to
approximately 5, and preferably approximately 2.5. The acidic
polishing slurry contains a chemical agent which preferentially
attacks the P2 pole tip material, such that the second CMP step
results in the recession of the upper surface of the P2 pole tip
relative to the dielectric layer surrounding it, as well as the
significant rounding of the upper edges of the dielectric trench in
which the P2 pole tip is formed. Thereafter, when the yoke is
plated onto the P2 pole tip the rounded upper edges of the
dielectric trench result in a concave curved interface between the
yoke and the P2 pole tip.
The resulting P2 pole tip/yoke interface possesses improved
magnetic flux flow control properties and results in decreased side
writing. Greater track per inch areal data storage results from the
reduced side writing of the improved write head.
It is an advantage of the magnetic head of the present invention
that increased areal data storage is obtained.
It is another advantage of the magnetic head of the present
invention that reduced side writing from the write head is
obtained.
It is a further advantage of the magnetic head of the present
invention that data tracks on magnetic media can be written closer
together because the side band noise created by side writing is
reduced.
It is a yet another advantage of the magnetic head of the present
invention that improved magnetic flux flow control through the P2
pole tip/yolk interface is obtained.
It is an advantage of the process for manufacturing a magnetic head
of the present invention that a second CMP polishing step on the
write head performed immediately following a first CMP polishing
step results in a magnetic head having improved performance
characteristics.
It is another advantage of the process for manufacturing a magnetic
head of the present invention that a second CMP polishing step on
the write head following a first CMP polishing step adds little to
the manufacturing time of the write head elements.
It is a further advantage of the process for manufacturing a
magnetic head of the present invention that a second CMP polishing
step following a first CMP polishing step adds little to the
manufacturing expense of the write head elements.
These and other features and advantages of the present invention
will become better known and understood upon reading the following
detailed description which makes reference to the several figures
of the drawings.
IN THE DRAWINGS
FIG. 1 is a side cross-sectional view presenting a schematic
illustration of a portion of a thin film magnetic head disposed on
a wafer substrate as configured during a process step executed in
the manufacturing thereof, as is known in the prior art;
FIGS. 2-8 depict the thin film magnetic write head elements of FIG.
1 in subsequent manufacturing process steps, as are known in the
prior art;
FIG. 9 depicts a new process step of the present invention executed
in the manufacturing of the thin film magnetic write head elements
of the present invention;
FIGS. 10-15 depict the thin film magnetic write head elements of
FIG. 9 in subsequent manufacturing process steps, as are known in
the prior art;
FIG. 16 is a perspective view of the thin film magnetic head of the
present invention including the improved P2 pole tip/yoke interface
thereof; and
FIG. 17 is a simplified top plan view of a hard disk drive
including the magnetic head of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Methods for manufacturing magnetic heads involve many process
steps, as are generally well known in the prior art, and FIGS. 1-8
and 10-15 generally depict prior art process steps involved in
depositing and removing of layers of various materials upon the
wafer surface, which steps ultimately result in the creation of a
plurality of write head components upon the wafer surface. The
write head components are subsequently separated and further
processed to become discrete thin film magnetic write heads. It is
important to note that not all write head. manufacturing process
steps are described herein, but only those process steps deemed
significant to the description and understanding of the present
invention. Additionally, while the detailed description herein is
directed to thin film magnetic write head elements, it is intended
that the invention and claims herebelow include thin film magnetic
heads that include read head components in addition to the write
head components described herein.
As is described in detail herebelow the new write head pole tip
includes an improved P2 pole tip/yolk interface that has improved
magnetic flux control properties which results in decreased side
writing. This allows for an increase in the areal density of data
storage on a disk by reducing the width of the noise band between
adjacent data tracks, such that the number of tracks per inch (TPI)
can be increased. A detailed description of the present invention
is next provided.
FIG. 1 is a side cross sectional view presenting a schematic
illustration of a portion of one of many write head components that
are in the process of being manufactured upon a wafer substrate,
and it will serve as the starting point for the description of the
present invention. As depicted in FIG. 1, a first pole (P1) 14 has
been formed on the wafer surface. Thereafter, a gap layer 18 has
been deposited upon the P1 pole tip, and a seed layer 22 has been
deposited upon the gap layer 18. The seed layer is generally
composed of the same material as a subsequently deposited second
pole tip material and serves to provide good adherence of the
subsequently deposited P2 pole tip material.
In the next process step, as depicted in FIG. 2, a resist plating
frame layer 26 is deposited upon the seed layer 22. Utilizing
standard photolithographic processing steps, a hole or trench 30 is
formed in the resist layer 26 for the subsequent deposition
(typically by electroplating) of the second pole tip (P2) 34.
Further openings 36 are formed in the resist plating frame layer
26, as is well known in the art. Thereafter, as depicted in FIG. 3,
the material that forms the P2 pole tip 34 is electroplated into
the trench 30 typically to a thickness less than the depth of the
trench 30, so as to prevent mushrooming of the P2 pole tip and the
openings 36 are also plated up with the material 38. The P2 pole
tip 34 may be composed of various materials as are known in the
art, with a nickel iron (NiFe) composition being specifically,
though not necessarily, used in the present invention. Thus the
seed layer 22 is also composed of NiFe.
Thereafter, as depicted in FIG. 4, the resist layer 26 is
chemically stripped, such that the P2 pole piece 34 the outer frame
pieces 38 and the seed layer 22 are exposed. Then, as depicted in
FIG. 5, the P2 pole tip and inner portions 40 of the seed layer 22
are covered by a shield layer 44, and a chemical etch process is
undertaken to remove the exposed outer frame pieces 38 as well as
portions of the seed layer 22. Thereafter, the shield layer 44 is
removed and the inner portions 40 of the seed layer are then
exposed, and the exposed inner seed layer portions 40 together with
any remaining seed layer portions are removed utilizing a
sputtering or ion milling tool. FIG. 6 depicts this stage in the
manufacturing process, wherein the P2 pole tip 34 and a portion 48
of the seed layer immediately below the pole tip 34 are disposed
upon the gap layer 18. It is to be noted that the preceding process
step description is a generalization and well known in the prior
art. Also, other and different process steps may be utilized to
achieve the resulting configuration depicted in FIG. 6.
Next, as depicted in FIG. 7, a layer of a dielectric material 60 is
deposited on the wafer surface. The layer 60 is typically though
not necessarily formed of alumina, and upwardly projecting portions
64 of the alumina layer 60 are formed wherever projecting P2 pole
tips are formed on the wafer. A first chemical mechanical polishing
(CMP) step is next conducted upon the wafer. The first CMP step
utilizes a relatively hard polishing pad and a chemical polishing
slurry that removes alumina and NiFe at approximately equal rates.
The slurry may have a neutral pH with a pasivating agent such as
BTA (benzothiazole), to a higher pH of approximately 10 where a
pasivating agent normally is not required. A chemical oxidant may
be included in the slurry, and a preferred oxidant is ammonium
persulfate. The relatively hard pad preferentially removes the
projecting portions 64 and the slurry attacks and remove the
alumina 60 and the NiFe that constitutes the P2 pole tip. The first
CMP step is conducted until the top surface 68 of each P2 pole tips
34 formed on the wafer is exposed within the polished surface 72 of
the alumina layer 60, as is depicted in FIG. 8.
All of the preceding process steps described hereabove and depicted
in FIGS. 1 through 8 are known and practiced in the prior art write
head pole tip manufacturing processes. They have been described
herein to provide a general background for understanding the
following process steps that comprise the novel features of the
present invention. Specifically, the significant step of the
present invention comprises the implementation of a second CMP
processing step at this point in the pole tip manufacturing
process, as is next described.
The second CMP step of the present invention involves the
utilization of a relatively soft polishing pad along with an acidic
polishing slurry. An oxidant, such as ammonium persulfate is
preferably included in the acidic polishing slurry. The acidic
polishing slurry coupled with the soft polishing pad of the second
CMP step create an environment in which the P2 pole tip is
preferentially attacked as compared to the alumina. As a result, as
depicted in FIG. 9, the second CMP step acts to remove the upper
surface 68 of the pole tip 34 to form a recessed P2 pole tip
surface 80. Additionally, the polishing action of the second CMP
step causes a rounding of the upper edges 84 of the alumina 60
above the surface 80 of the P2 pole tip 34. In the preferred
embodiment, the acidic CMP polishing slurry preferably has a pH of
from approximately 1 to approximately 5 with a preferred pH of
approximately 2.5. Generally, a more acidic polishing slurry will
more rapidly attack the NiFe pole tip material as compared to the
alumina, and a polishing slurry having a pH lower than
approximately 3 will generally cease to significantly remove
alumina, whereas a slurry having a pH higher than approximately 5
will remove excess alumina. Thus it is desirable to have a slurry
chemistry including a pH that is appropriate to attack the NiFe at
an acceptable rate while not attacking the alumina too greatly.
Owing to the small dimensions of the P2 pole tip, it is generally
desirable that the CMP polishing action of the pole tip be
conducted at least as rapidly as the chemical action of the acidic
slurry upon the pole tip. Where it is necessary to slow the
chemical attack of the acidic slurry upon the pole tip, an
oxidation inhibitor such as benzothiazole (BTA) may preferentially
be added to the acidic slurry to protect the P2 pole tip from
overreactive acid attack during the second CMP polishing step of
the present invention. The CMP polishing slurries described herein
are available from several commercial sources. One such source is
The Cabot Corporation, located in Aurora, Ill.; the preferred
acidic slurry of the second CMP step is designated as Semi Sperse W
2000.
Therefore, as depicted in FIG. 9, the result of the second CMP
polishing step of the present invention is that the upper surface
80 of the P2 pole tip is recessed into the alumina 60, and the
upper edges 84 of the alumina are rounded by the second CMP
polishing step. The degree of roundness of the edges 84 is somewhat
a function of the width of the P2 pole tip, and where a one micron
width P2 pole tip has undergone the second CMP polishing step of
the present invention, the pole tip surface 80 is recessed
approximately 0.3 microns and the rounded edges 84 of the alumina
have a radius of curvature of approximately 0.3 microns.
Following the second CMP polishing step of the present invention
the electromagnetic coils of the write head are next formed
utilizing many process steps that are generally known and utilized
in the prior art. These process steps are peripheral to the
invention described herein and will not be described in detail.
Thereafter, the yoke portion of the write head is formed onto the
P2 pole tip. Specifically, as depicted in FIG. 10, a second seed
layer 90 is deposited upon the surface of the wafer. The seed layer
90 covers the upper surface 80 of the P2 pole tip and serves to
provide good electromagnetic conduction between the yoke (to be
formed) and the upper surface 80. Thereafter, as depicted in FIG.
11, a resist layer 94 is deposited upon the seed layer 90 and
photolithographic steps are conducted to form a trench 98 into
which the yoke will be plated. Thereafter, as depicted in FIG. 12,
the yoke 104 is electrochemically plated into the trench 98 of the
resist layer 94.
Next, as depicted in FIG. 13, the resist layer 94 is removed to
expose the yoke 104 and the second seed layer 90. Thereafter, the
exposed seed layer 90 is removed utilizing process steps similar to
those described hereabove with regard to the first seed layer 22,
as depicted in FIGS. 4, 5 and 6. FIG. 14 depicts the device
following the removal of the exposed seed layer 90, such that only
the seed layer portions 108 between the P2 pole tip 34 and the yoke
104 remain. Thereafter, as depicted in FIG. 15, a further layer 120
of dielectric material such as alumina is deposited upon the wafer
surface, which typically results in the formation of projecting
portions 124 of the alumina layer 120. The completed write head
126, with a completed P2 pole tip/yoke interface 128 of the present
invention, is depicted in FIG. 15. The significant feature of the
P2 pole tip/yoke interface 128 of the present invention is the
curved surface 130 proximate the joinder of the P2 pole tip 34 and
the yoke 104. Specifically, the rounded upper edges 84 that are
created in the second CMP step of the present invention result in
corresponding concave rounded edges 130 of the yoke 104 at the
interface 128 between the P2 pole tip 34 and the yoke 104. These
concave rounded edges 130 of the present invention are to be
contrasted with the right angle interface between the P2 pole tip
and the yoke as is found in the prior art "T" type P2 pole
tips.
To provide a more complete understanding of the present invention
an isometric view with cutaway portions of the dielectric layers
(60 and 120) of the completed write head 126 of the present
invention is presented in FIG. 16. As depicted therein, the air
bearing surface (ABS) 160 of the write head 126 includes the P1
pole 14, the gap layer 18, the remaining first seed layer 48, the
P2 pole tip 34, the remaining second seed layer 90 and the yoke
104. The concave curved surface 130 of the P2 pole tip/yoke
interface 128 appears on the ABS surface and is formed proximate
all edges of the joinder between the P2 pole tip 34 and the yoke
104, including the side surfaces 164 of the P2 pole tip 34 and the
inner rearward surface 168. The magnetic flux generated within the
write head 126 passes through the interface 128 between the yoke
104 and the P2 pole tip 34, such that the interface 128 is both the
point of physical engagement and electromagnetic engagement of the
yoke 104 with the P2 pole tip 34. An advantage of the P2 pole
tip/yoke interface 128 of the present invention is that the
magnetic flux from the yoke 104 passes more efficiently into the
pole tip 34 than in the prior art "T" type P2 pole tip/yoke
interface configurations. Specifically, the sharp interior right
angle of the prior art "T" configuration inhibits the efficient
magnetic flux conduction between the yoke and the P2 pole tip, and
results in undesirable magnetic side writing through the unwanted
flow of magnetic flux directly from the yoke 104 to the P1 pole 14,
rather than the proper flow of magnetic flux from the yoke 104
through the P2 pole tip 34 to the P1 pole 14. The rounded concave
surfaces 130 of the P2 pole tip/yoke interface 128 of the present
invention therefore create a more efficient write head that has
reduced side writing, because the magnetic flux is more efficiently
channeled into the P2 pole tip 34 for the desired flux flow across
the write gap layer 18 from the P2 pole tip 34 to the P1 pole
14.
A simplified top plan view of a disk drive 180 that includes a thin
film magnetic head of the present invention is depicted in FIG. 17.
The disk drive 180 includes one or more hard disks 184 and one or
more actuator arms 188 that have a slider device 192 mounted
thereto. A magnetic head 126 of the present invention is formed on
a surface of the slider member utilizing the manufacturing
techniques described hereabove. As is well known to those skilled
in the art, the disk drive 180 includes additional
electromechanical and computerized components (not shown).
While the present invention has been shown and described with
regard to certain preferred embodiments, it will be understood by
those skilled in the art upon reading the preceding disclosure that
certain alterations and modifications in form and detail may be
made therein. It is therefore intended by the inventors that the
following claims cover all such alterations and modifications that
nevertheless include the true spirit and scope of the
invention.
* * * * *